President Donald Trump reimposed sanctions on Iran's energy and finance sectors on November 5 following his May decision to abandon a landmark 2015 nuclear deal between major powers and Tehran.
But he gave Iraq a 45-day waiver to continue buying electricity and natural gas to generate it from its eastern neighbor, Middle East Online reported.
Iraq was expected to use that time to submit a plan on how it would wean itself off Iranian supplies.
In the days leading up to the deadline Thursday, Prime Minister Adel Abdel Mahdi said a delegation of Iraqi officials would travel to Washington to discuss sanctions.
And on Thursday, a government source involved in the talks, said the delegation had secured a 90-day extension so Iraq could keep buying both Iranian electricity and gas.
Asked whether the US had pressured the Iraqi delegation to partner with US companies to fill the eventual gap, the source said the issue was part of "complicated discussions".
Iraq faces a chronic power shortage that often leave homes without mains electricity for as much 20 hours a day and was a key driving factor behind mass protests this summer.
To cope with the shortages, Iraq pipes in up to 28 million cubic metres of Iranian gas a day for power generation and also directly imports up to 1,300 megawatts of Iranian electricity.
That dependence is uncomfortable for Washington, which sees Tehran as its top regional foe.
Last week, US Energy Secretary Rick Perry discussed sanctions with Iraq's ministers of oil and electricity in Baghdad, and said Iraq should partner with US companies to become energy independent.